Aqueous basic solutions of phenolic resins are known in the art. They are used in making foundry mixes which are made into foundry shapes. The shapes are cured with an ester co-reactant by a no-bake or cold-box process depending upon whether a volatile ester is used for curing.
Although these processes have advantages from an environmental standpoint, they also have limitations. One of the primary limitations is that the tensile strengths and scratch hardness are lower than for some of the other no-bake and cold-box processes used for preparing workable foundry shapes.
Furthermore, the stability of these aqueous basic solutions of phenolic resole resins is primarily dependent upon using large quantities of base, particularly potassium hydroxide.
The use of large quantities of potassium hydroxide makes it difficult to reclaim the sand used in making the foundry shapes. This is wasteful and creates stress to the environment.
European patent application 0 336 533 discloses that reclaimed sand derived from dismantled foundry shapes made with aqueous alkaline phenolic resole resins can be effectively used to make foundry shapes if a silane is added to the reclaimed sand prior to adding the resin and ester co-reactant. Silanes, however, are expensive and more economical methods of using reclaimed sand are needed.